For many years solvents such as hydrogen peroxide, bleach and other like chemical liquids have been sold in blow molded plastic containers. Due to the fact that these containers are mass-produced in halves which are brought together to form bottles having longitudinal seams along the mold lines, the bottle halves are often slightly misaligned and as a result the bottle openings include a somewhat non-planar abutting closure surface. Thus, these containers often have openings provided with one region of the closure surface higher in elevation than the adjacent surface. As a result, closures and caps abutted thereto have a tendency to incompletely seal, and as a result to leak the liquid from within the container.
Indeed, other types of bottles may also have openings which are not entirely uniform, and this can occur regardless of how the bottle is formed. Even with glass bottles, the uniformity of the bottle neck may be sufficiently irregular so that sealing with the bottle cap is imperfect. This problem sometimes arises in glass bottles in the form of an oval rather than a circular neck. Thus, while the problem is particularly acute in plastic bottles which are formed between mating mold halves, the problem of irregular bottle openings can occur in any kind of bottle.
Attempts have been made over the years to place or insert a disk or gasket or liner within the cap to insure a proper seal between the cap and the surface of the bottle opening. For example, U.S. Pat. Nos. 4,256,234 to Mori et al; 4,351,443 to Uhlig; and 4,476,987 to Nolan all show container closures or caps provided with gasket inserts to facilitate a seal between the cap and the container's opening surface. Other patents of the same general type are Breskin U.S. Pat. No. 4,489,844; Banich U.S. Pat. No. 4,346,812; Kornelis U.S. Pat. No. 4,244,481 and Ostrowsky U.S. Pat. No. 4,427,126. These above-mentioned patents concern gaskets which abut directly against the cap's bottom wall and therefore do not solve the aforementioned problem of providing proper seal in containers having uneven closure opening surfaces.
A particularly satisfactory product of the prior art is disclosed in the Williams U.S. Pat. No. 3,612,325. This patent discloses a liner inserted adjacent the bottom wall of a bottle closure in such a way as to be allowed to rotate independently of the closure, so that the sealing bottle edge does not scrape or rotate with respect to the bottle top. When the liner does not turn with the closure but is able to rotate, it is able to seal vertically on the bottle top. With a flash line on the top of the bottle, the liner approaches the flash vertically and does not rotate over the flash line thereby causing the seal to stick or bear against the flash line.
Nevertheless, in spite of this superior functioning, in extreme cases of the aforementioned imperfections, the semi-floating seal of the Williams '325 patent is not sufficient. Thus, it has been proposed to use a very thick liner, which may be as thick 1/8 to 1/4-inch or more, to fill the voids and cracks caused by whatever imperfection in the bottle top may exist. Such thick liners require additional cap height as well as the additional liner thickness, both of which add expense to the product. Not only does this additional expense occur on bottles with imperfections, but also the expense occurs on bottles that have a minimum of imperfections because it is uneconomical to sort the good bottles from the bad ones and use different types of caps and liners for each group. Thus, all bottles require the additional expense, needed or not.
In addition to the expense of the added height of the cap and thickness of the liner, there is a further complication because bottle capping machines have a torque setting that requires constant adjustment depending on the variable amounts of friction the imperfections impart to a thick liner. Standards in the industry require certain amounts of application torque and backoff torque, and a thick liner complicates this adjustment.
Unlike the Williams U.S. Pat. No. '325, the patent to Herbert U.S. Pat. No. 4,564,117 provides means for preventing rotation of the liner gasket relative to the cap. This defeats the beneficial results of the Williams U.S. Pat. No. '325 as mentioned above. These means take the form of shallow, rounded annular ribs located directly above the edge of the bottle top. As illustrated in the left-hand portion of the sole figure, upon tightening the cap the annular ribs project into the surface of the gasket and prevent its rotation relative to the cap.
Thus, the art has so far failed to provide a satisfactory solution to the problem outlined above resulting from imperfections which occur during formation of the bottle.